Hosted application sandbox model

ABSTRACT

An application host (such as a web application server) may execute a set of applications on behalf of a set of users. Such applications may not be fully trusted, and a two-way isolation of the distributed resources of an application (e.g., the executing application, the application user interface on the user&#39;s computer, and server- and client-side stored resources) from other applications may be desirable. This isolation may be promoted utilizing the cross-domain restriction policies of each user&#39;s computer by allocating a distinct subdomain of the application host for each application. The routing of network requests to a large number of distinct subdomains may be economized by mapping all distinct subdomains to the address of the domain of the application host. Moreover, the application user interfaces may be embedded in an isolation construct (e.g., an IFRAME HTML element) to promote two-way isolation among application user interfaces and client-side application resources.

CROSS-REFERENCE TO RELATED CASES

The present application is a continuation of and claims priority to U.S.patent application Ser. No. 12/429,954, filed on Apr. 24, 2009 and alsoentitled “Hosted Application Sandbox Model,” the entirety of which ishereby incorporated by reference as if fully rewritten herein.

BACKGROUND

In the field of computing, an application may be executed by anapplication host, such as a web application executed by a webapplication server and communicating with a user through web pagesrendered in a web browser. The application host may offer several suchapplications, and may embed several applications in the same web page.Each application may be configured to access a particular set ofresources on the application host, including application resources(e.g., application binaries and configuration information), applicationprogramming interfaces and libraries provided by the application host,and data objects generated by the user and accessible to the applicationhost.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key factors oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

An application host may be configured to execute a variety ofapplications, including applications that are developed by thirdparties. Such third parties may be untrusted or even unknown, and theapplications generated thereby may contain faulty or maliciousoperations that steal a user's data objects, corrupt the applicationhost, and/or waste resources. Such applications may also be capable ofinterfering with other applications executing on the application host,or with applications executing on the user's computer. For example, if aweb page embeds two applications that execute in a user's web browser,the first application might (through misconfiguration or maliciousdesign) interfere with the execution of the second application byquerying for and operating on document elements associated with thesecond application, by interacting with the cookies of the secondapplication stored in the user's web browser, or by monitoring oraltering the communication of the second application with theapplication host of the second application.

In order to reduce vulnerabilities of hosted applications, anapplication host may utilize a cross-domain restriction policyimplemented on the client, such as a same-origin policy implemented bythe web browser of the computer. Such restrictions restrict anapplication to accessing resources associated with the subdomain towhich the application belongs. For example, an application may onlyaccess remote resources that are hosted within the particular subdomain,and a web application may only access elements within the web documentthat are associated with the particular subdomain.

An application host may utilize these client-side policies in order topromote the isolation of hosted applications, both at the server (suchas receiving and processing requested operations and granting access toserver-side resources) and at the client (such as restricting theinteraction of the application with other applications hosted by thesame application host and embedded in the same web page.) One suchtechnique involves allocating a distinct subdomain for each hostedapplication, such as “app1.host.com” and “app2.host.com,” so that thecross-domain restrictions may effectively isolate these applicationswhile executing on the client. However, it may be difficult for theapplication host (such as routing hardware) to contend with a largenumber of subdomains, particularly where the application host offersdozens or hundreds of hosted applications. Therefore, the applicationhost may also map all of the distinct subdomains to a single networkaddress, so that the requests may be similarly routed to the applicationserver even if identified by different subdomains. Additional techniquesmay also be utilized, such as rendering an embedded web applicationwithin an isolation construct (e.g., a HyperText Markup Language [HTML]IFRAME element) that promotes the application of cross-domainrestrictions by the user's computer (such as the client-side webbrowser), and by implementing a permission token mechanism (such as acryptographically signed cookie) that indicates the permissions that auser may have authorized for the application to access his or her dataat the application host.

To the accomplishment of the foregoing and related ends, the followingdescription and annexed drawings set forth certain illustrative aspectsand implementations. These are indicative of but a few of the variousways in which one or more aspects may be employed. Other aspects,advantages, and novel features of the disclosure will become apparentfrom the following detailed description when considered in conjunctionwith the annexed drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an exemplary scenario of an applicationhost configured to execute an application on behalf of a user.

FIG. 2 is an illustration of an exemplary scenario of a web applicationserver configured to execute a web application on behalf of a user, andto present a web application user interface to the user embedded in aweb page presented by a web browser.

FIG. 3 is an illustration of an exemplary scenario of an applicationhost configured to execute a set of applications on behalf of a set ofusers.

FIG. 4 is an illustration of an exemplary web page wherein severalapplication user interfaces have been embedded.

FIG. 5 is an illustration of an exemplary system configured to executean application on an application host on behalf of a user of a computer.

FIG. 6 is an illustration of an exemplary computer-readable mediumcomprising processor-executable instructions configured to embody one ormore of the provisions set forth herein.

FIG. 7 is an illustration of an exemplary deployable computingenvironment wherein the techniques discussed herein may be implemented.

FIG. 8 illustrates an exemplary computing environment wherein one ormore of the provisions set forth herein may be implemented.

DETAILED DESCRIPTION

The claimed subject matter is now described with reference to thedrawings, wherein like reference numerals are used to refer to likeelements throughout. In the following description, for purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the claimed subject matter. It may beevident, however, that the claimed subject matter may be practicedwithout these specific details. In other instances, structures anddevices are shown in block diagram form in order to facilitatedescribing the claimed subject matter.

In the field of computing, an application may be hosted by anapplication host to be executed on behalf of a user of a computer in aserver-client arrangement. As one example, a web application may beprovided by an application web server that generates one or morewebpages that are delivered to the computer to be rendered and displayedfor the user within a web browser. As another example, an applicationserver may remotely execute an application and may send instructions tothe computer to render a user interface for the user that accepts inputand displays output. Each computer may have a network address, andcommunication therebetween may be arranged according to variousprotocols (which may comprise, e.g., one or more implementations ofvarious layers of a network stack.) The execution of the application maybe allocated in various ways over the computing resources of theapplication host and the user's computer, and possibly over those ofother computers. For example, a thin-client architecture may allocate alarge portion of the application processing to the application host andmay allocate to the client only basic input and output functions.Alternatively, the application may involve some client-side processing,wherein I/O pre- or post-processing or portions of business-logicprocessing may be performed by the user's computer. The application hostand the user's computer are often connected over a network, such as theinternet or a local area network.

FIG. 1 illustrates a first exemplary scenario 10 involving anapplication host 12 configured to execute an application 16 on behalf ofa user 20 of a computer 22, where the application host 12 and thecomputer 22 represent a server-client relationship. The application host12 stores the application 16 in an application store 14, such as anexecutable (e.g., a script, a compiled library or assembly, or anapplication markup document formatted according to XAML) stored in aportion of the file system of the application host 12. The applicationhost 12 may also be capable of communicating with the computer 22 over anetwork 24, such as the internet, a local area network (LAN), or acellular network. Moreover, the application host 12 and the computer 22may each have a network address 26, 28 that distinctively identifies(respectively) the application host 12 and the computer 22 foraddressing and identifying messages exchanges over the network 24. Theuser 20 may send a request 30 to the application host 12 over thenetwork 24 to execute the application 16, which may generate an instanceof the application 16 and commence execution. The application 16 maycommunicate with the user 20 through a rendering of an application userinterface 34 on the computer 22 that may be configured to receive inputfrom the user 20 that may be forwarded to the application 16 executingon the application host 12 and/or to generate output to be rendered onthe computer 22 for the user 20. The application 16 may generate theapplication user interface 34 on the computer 22 by sending instructions32 over the network 24 for rendering the application user interface 34,such as an Extensible Application Markup Language (XAML) document thatmodels the controls and layout of the application user interface 34 andindicates how input received from the user 20 may be handled. Moreover,the instructions 32 may also allocate a portion of the processing of theapplication 16 to the computer 22; e.g., it may be more efficient toperform some input pre-processing and/or output post-processing of theapplication 16 on the computer 22 rather than on the application host12. The exemplary scenario 10 therefore models a typical hosting andexecution of an application 16 by an application host 12 on behalf of auser 20 of a computer 22.

FIG. 2 illustrates a more specific and detailed example 40 that involvesa web application 46 hosted by a web application server 42 and stored ina web application store 44. The web application 46 is configured topresent the application user interface 56 within a web browser 50executing on the computer 22 operated by the user 20. More specifically,the web application 46 is embedded in a web page 54, such as in ahypertext markup language (HTML) document sent to and rendered by theweb browser 50 in response to a hypertext transfer protocol (HTTP)request 52 initiated by the user 20 (e.g., a request to visit aparticular uniform resource locator [URL] associated with the webapplication 46.) The web application host 42 may therefore fulfillrequests to execute the web application 46 by implementing an HTMLrendering component 48 that, upon receiving the HTTP request 52, invokesthe web application 46 to execute on the web application host 42, andembeds any HTML generated by the web application 46 representing anapplication user interface 56 in a web page 54 delivered to the webbrowser 50. The web browser 50 then renders the web page 54, includingthe web application interface 56, and may forward input received fromthe user 20 to the web application host 42 (and in particular to the webapplication 46) for further processing. The web browser 50 may alsopermit the web application 46 to perform other actions, such asinteracting with a web application resource 58 (e.g., a programminglibrary, database, web service, or privately hosted process executing onthe web application host 42) and/or configuring the application userinterface 56 to store one or more application cookies 62 in a browsercache 60 associated with the web browser 50 in order to persist dataacross requests and sessions of the web application 46 and/or the webbrowser 50.

In more complex scenarios, an application host 12 may host more than oneapplication 16, such as an email application and a chat application.Moreover, these applications may be executed concurrently on theapplication host 12, and the application user interfaces 34 may becombined into a user interface that is presented to the user 20. Forexample, a web page 54 may embed both an email application and a chatapplication that may be presented to the user 20 in an application userinterface 34, such as an HTML document embedding elements of eachapplication 16. In addition, the application host 12 may concurrentlyand/or consecutively execute one or more applications 16 on behalf ofmultiple users, such as a set of web visitors that each wish to executea particular application 16. Moreover, an application 16 may interactwith a particular set of resources, such as a database hosted by theapplication host 12. In even more complex scenarios, respectiveapplications 16 may interface with distinct sets of applicationresources, and perhaps even resources exclusive to one or moreapplications 16 and/or users 20. For example, an application 16 mayinteract with a particular application resource stored on theapplication host 12, included in the application user interface 34(e.g., a control embedded in a web page 54), and/or stored on thecomputer 22 (e.g., an application cookie 62 specific to the application16.) It may be desirable to restrict other users 20, computers, andapplications 16 from accessing such application resources. For example,an application 16 may store on the application host 12 a private dataset, such as an email mailbox; may present the private data to the user20 through a protected control in the application user interface 34,such as an email interface; and may store on the computer 22 privatedata of the user 20 for the application 16, such as authenticationcredentials to login to the application 16. The security of thisapplication 16 and the associated user data may be compromised if otherusers 20, other applications 16, or even other instances of the sameapplication 16 (e.g., other instances of an email client operated byother users 20) are able to access the private data stored on theapplication host 12 or the computer 22 or eavesdrop on the protectedcontrol within the application user interface 34.

FIG. 3 illustrates an exemplary scenario 70 wherein a first user 72 anda second user 74 interact with a set of applications hosted on variousapplication hosts. A first application host 76 may comprise anapplication store 78 (which may resemble, e.g., the application store 14of FIG. 1, and may be similarly configured in various aspects)containing a first application 80 (which may be implemented, e.g., in afirst application executable.) This first application 80 stores in theapplication store 78 of the first application host 76 a per-user set ofresources, such as a first user resource 82 for the first user 72 and asecond user resource 84 for the second user 74. The application store 78of the first application host 76 also stores a second application 86,which also stores a first user resource 88 and a second user resource90. The first application host 76 may present these applications torespective users in a user interface, such as a web page embedding aplurality of applications, which may be generated by an applicationrendering component 92. Moreover, the user interface may present theseapplications in various combinations, such as a set of interrelatedapplications that cooperatively provide a set of capabilities, a set ofloosely interrelated applications that may interact in a simple manner,or as disassociated applications that are presented within the same userinterface but that are visually and functionally isolated. The userinterface may be transmitted to the computers operated by these users(such as a first computer 94 operated by the first user 72 and a secondcomputer 96 operated by the second user 74) for rendering thereupon.These computers may communicate over a network 98, such as the internet,a local area network, or a cellular network, wherein the firstapplication host 98 may have a first application host network address100 (such as an IP address in an IP-based network), the first computer94 may have a first computer network address 102, and the secondcomputer 96 may have a second computer network address 104.

The computers of the users may be configured to present the applicationsexecuting on behalf of the users within respective application userinterfaces. For example, the first computer 94 may present anapplication user interface 106 embodying both a first application userinterface 108 of the first application 80 (which may render the datastored in the first user resource 82 of the first application 80) and asecond application user interface 110 (which may render the data storedin the first user resource 88 of the second application 86.) Moreover,these application user interfaces may be configured to store variousdata objects on the computer 94 (e.g., as cookies stored in a browsercache of a web browser executing on the respective computers); such dataobjects may comprise, e.g., a first local user resource 112 generated bythe first application 80 and a first local user resource 114 generatedby the second application 86. Similarly, the second computer 96 mayrender and present to the second user 74 an application user interface116 comprising a first application interface 118 corresponding to thefirst application 80 (which may render the second user resource 84 ofthe first application 80) and a second application interface 120 for thesecond application 86 (which may render the second user resource 90 ofthe second application 86); and, again, such application user interfacesmay be configured to store local application resources on the secondcomputer 96 a second local user resource 122 belonging to the firstapplication 80, and a second local user resource 124 belonging to thesecond application 86.

Finally, the first user 72 and the second user 74 may also interact witha third application 130 hosted by a second application host 126. Thisthird application 130 may be stored in an application store 128 of thesecond application host 126, along with a first user resource 132 and asecond user resource 134 respectively associated with the first user 72and the second user 74. Again, the application store 128 of the secondapplication host 126 might resemble the application store 14 of FIG. 1,and may be similarly configured in various aspects. The secondapplication host 126 may also render (e.g., by an application renderingcomponent 136 of the second application host 126) a third applicationuser interface for the third application 130 that may be included in theapplication user interface 106 of the first computer 94 and theapplication user interface 116 of the second computer 96, which may betransmitted to the first computer 94 and the second computer 96 over thenetwork 98 (e.g., by sending the respective application user interfacesto the first computer network address 102 and the second computernetwork address 104 from a second application host network address 138.)Although not expressly illustrated in FIG. 3, it may be appreciated thatthe third application user interface of the third application 130 may becombined with the first application user interface 108 and the secondapplication user interface 110 in respective application userinterfaces. Additionally, although also not so illustrated in FIG. 3,the third application 130 may store local application resources forrespective users on the first computer 94 and the second computer 96.

In this manner, the computers of the respective users may assemble acomposite application user interface, comprising application userinterfaces for three distinct applications (two hosted on the firstapplication host 76 and one hosted on the second application host 126.)Moreover, each application user interface may render private data forthe respective users stored on the respective application hosts, and maybe permitted to store data objects locally (such as cookies in thebrowser caches of the respective machines) in order to persist data overinstances of the respective applications and the web browsers. FIG. 4illustrates an exemplary scenario 140 of a web page 54 rendered in a webbrowser 50 on behalf of a user 20 and comprising a web applicationinterface embedding a first application user interface 142 of a firstweb application, a second application user interface 144 of a second webapplication, and a third application user interface 146 of a third webapplication. Moreover, each application user interface may renderprivate data of the user 20, which may be stored remotely (e.g., by theapplication host) or locally (e.g., as a cookie stored in the browsercache of the web browser 50, a file stored in a file system of thecomputer 22, a registry key stored in a system registry of the computer22, or an application resource stored in an offline browser applicationcache implemented according to the HTML 5 standard), thereby presentinga personalized application experience. However, such web applicationsmay be hosted by different application hosts; e.g., a first applicationhost 76 may host the first web application and the second webapplication, and may transmit to the web browser 50 the firstapplication user interface 142 and the second application user interface144, while a second application host 126 may host the third webapplication and may present the third application user interface 146.Despite the various hosting sources of the applications, the transmittedapplication user interfaces may be combined in the web page 54 andrendered together by the web browser 50 to present an application userinterface to the user 20. The application user interface may present theapplications in visual and/or functional isolation (e.g., withinseparate visual containers and configured to function independently), orwith degrees of interoperation (e.g., as related visual components of asingle composite application, or functionally cooperating to achieve adesired result.)

However, in complex scenarios such as the exemplary scenario 70 of FIG.3, a great number and variety of security risks may arise. As a firstexample, a first application 80 might permit a first user 72 to accessthe second user resource 84, comprising the private data of the seconduser 74 hosted on the first application host 76, thereby exposing theprivate data of the second user 74 to the first user 72. As a secondexample, the first application 80 may be permitted to access the firstuser resource 88 of the second application 86 stored on the firstapplication host 76, and/or the first local user resource 114 of thesecond application 86 stored on the first computer 94, therebyinterfering with the execution of the second application 86 andpotentially leaking private data that the first user 72 expected to berestricted to the second application 86 into the first application 80.As a third example, the first application user interface 108 of thefirst application 80 executing within the application user interface 106on the first computer 94 may be permitted to access the secondapplication user interface 110 of the second application 86 (e.g., byaccessing HTML document elements belonging to the second application 86that are embedded in the composite web page), thereby permitting thefirst application 80 to monitor and/or interfere with the properexecution of the second application user interface 110 on the firstcomputer 94. As a fourth example, the third application 130 executing onthe second application host 126 may be permitted to access variousresources of the first application host 76 (such as the user resourcesstored in the application store 78 of the first application host 76)and/or features of applications hosted by the first application host 76but executing on the first computer 94 of the first user 72 (e.g., athird application user interface may be permitted to interact with theapplication user interfaces of the applications hosted by the firstapplication host 76 or the locally stored user resources of suchapplications.) As a fifth example, an application user interfaceexecuting on the first computer 94 may be able to gain access to aspectsof the second computer 96, e.g., by sharing the second computer networkaddress 104 and allowing the user interfaces of an application executingon the respective computers to communicate and share the data of thesecond user 74 with the first user 72. It may be appreciated that manyscenarios in the field of computing may be as complex or more complex asthe exemplary scenario 70 of FIG. 3 (e.g., peer-to-peer distributedcomputing applications), and many types of vulnerabilities may beidentified and exploited by malfunctioning or maliciously designedapplications and computers.

Some of these vulnerabilities may be reduced by the implementation ofcross-domain restriction policies, whereby an application (such as a webapplication) identifies a domain to which it belongs, and is restrictedto accessing resources belonging to the same domain. A computer may,upon receiving or creating a resource on behalf of an application,associate such actions and data objects with the domain from whence theapplication was received. The application may thereafter be restrictedto accessing resources associated with the same domain, and precludedfrom accessing resources associated with other domains. Cross-domainrestriction policies are often implemented on computers in the contextof executing untrusted applications. In particular, web browsers oftenimplement a same origin policy that examines the domains associated withvarious web requests of executing applications and restrictsapplications to interacting with resources and servers within the samedomain. The same origin policy is utilized by comparing the protocol,subdomain, and domain of a requested web resource with the protocol,subdomain, and domain of the requesting application in order todetermine whether to permit or restrict the request.

For example, in FIG. 3, the first application 80 and the secondapplication 86 are received from the first application host 76, whichlikely specifies a particular domain (e.g., “host1.com”), while thethird application 130 is received from the second application host 126that likely specifies a different particular domain (e.g., “host2.com”).For example, when the first application user interface 108 is receivedfrom the first application host 76 on behalf of the first application80, the first application user interface 108 is associated with thedomain of the first application host 76 (e.g., “host1.com”), and theresources of the first application 80, including the first user resource82 and the first local user resource 112, are also associated with thesame domain. When the first application user interface 108 attempts toaccess such resources, the first computer 94 may examine the associateddomains and permit the operation. However, if the third application 130,which is associated with the domain of the second application host 126(e.g., “host2.com”) or an application user interface of the thirdapplication 130 attempts to access these resources of the firstapplication 80, the first computer 94 may examine the associateddomains, identify a mismatch, and restrict the accessing.

However, the configuration of the applications may vary the degree towhich security issues may be reduced by cross-domain restrictionpolicies. Again referring to FIG. 3, the first application host 76 maybe configured to host various applications (including the firstapplication 80 and the second application 86) at different addresses(such as URLs) within the same domain. For example, if the firstapplication host 76 comprises the “host1.com” domain, the firstapplication 80 may be located at a first location within the domain,such as “http://host1.com/app1”, while the second application 86 may belocated at a second location within the domain, such as“http://host1.com/app2”. This configuration may reflect a logicalarrangement of the applications on the first application host 76; e.g.,the organization of the URLs may reflect the organization ofcorresponding files within the filesystem of the first application host76 as a webserver, or to a first server (hosting the first application80) and a second server (hosting the second application 86) in adistributed server configuration. Because these applications are hostedby the first application host 76, the resources of such applications(both stored on the first application host 76 and on various computers,such as the local user resources stored on first computer 94) areprotected by cross-domain restriction policies from interference fromapplications hosted by other application hosts, such as the secondapplication host 126. However, because the applications are hostedwithin the same domain (“host1.com”), and also within the same subdomainand accessible through the same protocol (in this example, HTTP), theapplications may be able to interact with each other. For example,cross-domain restriction policies, such as the same origin policyimplemented on web browsers, do not preclude the first application 80executing on the first application host 76 from accessing the secondapplication 86 hosted on the application host 76 or the application userresources of the second application 86 (such as the first user resource88 of the second application 86.) Such policies also do not restrict thefirst application user interface 108 executing on the first computer 94from interfering with the second application user interface 110, oraccessing the first local user resource 114 of the second application 86stored on the first computer 94.

Techniques may be developed to promote the isolation of an application16 hosted by an application host 12 and interfacing with a user 20through an application user interface 34 of a computer 22. Suchtechniques may be particularly useful, e.g., where an application host12 is configured to host applications received from third parties, whichmay not be as fully trusted as applications developed by theadministrators of the application host 12. For example, a website mayserve as an application platform that allows users to install andutilize a set of web applications 46, potentially including webapplications 46 received from third parties (either directly received bythe web application host 42 and offered to users 20, or received from auser 20 who may wish to use the web application 46.) It may be desirableto configure the web application host 42 to isolate an application fromaccessing the resources of other applications, including on the webapplication host 42, within the web browser 50 (such as accessing HTMLelements of other applications embedded in the same web page 54), andelsewhere within the computer 22 (such as cookies of other webapplications 46 stored in the browser cache 60.) Moreover, it may beadvantageous to utilize currently implemented security mechanisms of thevarious components of this distributed system (such as may beimplemented the application host 12, the application store 14, thecomputer 22 of the user 20, the web browser 50, and the browser cache60) instead of depending on new security mechanisms that may bepartially, inconsistently, or less than ubiquitously implemented. Inparticular, it may be advantageous to base such techniques oncross-domain restriction policies that extend to several aspects of suchapplications 16 (e.g., the elements of an application within an HTMLdocument, the process hosting the application 16 on the computer 22,client-side resources of the application 16 such as application cookies62, the application hosts 12 that the application 16 is permitted tocontact, and the resources of an application host 12 that theapplication 16 is permitted to utilize.) Security models based on thismodel may apply to the entire set of resources utilized by anapplication 16, and may permit the application 16 to access this broadset of resources associated with the domain while restricting access tounrelated resources, thereby providing pervasive, two-way isolation ofthe application 16.

One such technique relates to the association of domains with the set ofapplications 16 hosted by an application host 12. An application host 12may expose applications 16 at various locations associated with theapplication host 12, but in a manner that takes advantage of thecross-domain restriction policies to promote the isolation of anapplication 16 from other applications 16 stored on the same applicationhost 12 (as well as applications 16 stored on other application hosts 12and locally executed on the computer 22.) Specifically, the applicationhost 12 may be configured to allocate a subdomain of the domain of theapplication host 12 for an application 16. For example, with referenceto FIG. 3, if the first application host 76 is associated with the“host1.com” domain, the first application 80 may be associated with thesubdomain “app1.host1.com”, and the second application 86 may beassociated with the subdomain “app2.host1.com”. If a subdomain isallocated for respective applications 16, then an application 16(including all of its associated resources on the application host 12and on the computer 22, such as the application user interface 34,elements of the application 16 embedded in a web page 54, andapplication resources stored on the computer 22, such as applicationcookies 62 stored in a browser cache 60) may be isolated from access byother applications 16, even those hosted on the same application host 12but at a different subdomain, due to the cross-domain restrictionpolicies implemented in various systems of the application host 12 andthe computer 22. Moreover, distinct subdomains may be generated fordifferent instances of the same application 16, such as a first instanceexecuting on behalf of a first user 72 and a second instance executingon behalf of a second user 74.

However, this technique may raise difficulties with network management,because the number of subdomains associated with a particular domain ofan application host 12 may grow to an unmanageable number and/or maychange with an unmanageable frequency. For example, if an applicationhost 12 hosts and executes one hundred applications 16 on behalf of onehundred users 20, and if each instance of an application 16 on behalf ofeach user 20 is allocated a distinct subdomain, the domain of theapplication host 12 may contain 10,000 subdomains. Routing hardwareservicing the application host 12 may have considerable difficultytracking the use of such subdomains; e.g., the routing tables used bysuch routing hardware may become significantly encumbered, therebyutilizing more computing resources and/or providing lower-qualityservice while contending with the vast number of subdomains. In view ofthis potential difficulty, this application isolation technique may alsoinvolve unifying the routing of the subdomains. For example, a singledomain name server (DNS) entry may be created that maps all subdomains(e.g., “*.host1.com”) to the network address 26 of the application host26. This mapping may permit routing hardware to handle the wide varietyof subdomain accesses to hosted applications 16 in an efficient manner.Moreover, new subdomains may be generated (e.g., a new subdomain for anew application 16, or for a new instance of an application 16) and maybe properly routed without having to update the DNS entry mapping allsubdomains to the same application host 12. Other advantages may alsoflow from this technique (e.g., if two applications 16 happen to utilizethe same resource, e.g., “app1.host1.com/Shared Resource” and“app2.host1.com/SharedResource”), the translation of both subdomains tothe same network address (such as the IP address of host1.com) maypermit the computer 22 to identify that a resource was previouslyaccessed by another application 16, and to refer to a copy of theresource in a local cache.

FIG. 5 illustrates an exemplary scenario 150 applying this technique asan implementation of an application host 12 that is configured toexecute one or more applications 16 on behalf of one or more users 20,each operating a computer 22 connected to the application host 12 over anetwork 24 and configured to present various application interfaces ofthe corresponding applications 16 that are executing on the applicationhost 12. These application interfaces may issue requests to theapplication host 12 over the network 24, such as interfacing with theexecuting applications 20 and accessing remotely stored resources. Inview of this scenario, the application host 12 may facilitate theregistering and execution of applications in a manner that promotes theisolation of respective applications 20. The applications stored in theapplication store 14 may be assigned distinct subdomains, such as afirst distinct subdomain 158 (e.g., “app1.host1.com”) allocated for thefirst application 80 and a second distinct subdomain 160 (e.g.,“app2.host1.com”) allocated for the second application 86. Moreover,these subdomains may be mapped to the network address of the applicationhost 12. Accordingly, in the exemplary scenario 150 of FIG. 5, theapplication host 12 incorporates an exemplary system 152 configured toexecute various applications on behalf of users of computers. Theexemplary system 152 of FIG. 5 includes an application store 14 that isconfigured to store applications 20, such as a first application 80comprising a first application executable 154 (e.g., a script, acompiled library or assembly, or an application markup documentformatted according to XAML) and a first application resource (e.g., adatabase, a media object, or a help document displayed within theapplication), and a second application 86 comprising a secondapplication executable 156 and a second application resource. Theexemplary system 14 also comprises an application registering component162 that is configured to allocate a distinct subdomain of the exemplarysystem 14 for respective applications, where each such distinctsubdomain is mapped to the network address of the exemplary system 14.Finally, the exemplary system 14 comprises an application executingcomponent 164 that is configured to, upon receiving a request to executean application on behalf of a user (such as the user 20 of the computer22), execute the application 16 on the exemplary system 14, and topresent to the user 20 an application user interface of the applicationserved from the distinct subdomain.

In the exemplary scenario 150 of FIG. 5, the exemplary system 152functions in the following manner. When an application 16 is registeredwith the application host 12, such as when the application resources ofthe first application 80 (including a first application executable 154and a first application resource), the application registering component162 allocates for the first application 80 a distinct subdomain of thedomain of the application host 12. For example, if the application host12 services the “host1.com” domain, the first application 80 may beallocated the “app1.host1.com” subdomain, and may be accessible athttp://app1.host1.com. Moreover, the application registering component162 maps this distinct subdomain to the same IP address as the domain ofthe application host 12, e.g., 207.46.30.34. Similarly, when the secondapplication 86 is received and stored in the application store 14, theapplication registering component 162 allocates the “app2.host1.com”distinct subdomain for the second application 86, which is also mappedto the same IP address as the domain of the application host 12. In thisexemplary scenario 150, a user 20 of a computer 22 may thereafterrequest to execute both applications, along with a third applicationhosted by a different application host, such as by directing a webbrowser executing on the computer 22 to access a web page embedding theapplication user interfaces of all three hosted applications. Forexample, when the user 20 invokes the first application 80, the computer22 sends a request to the application host 12 over the network 24 toexecute the first application 80. The application executing component164 thereby generates an executing instance of the first application 80and sends to the computer 22 over the network 24 a first applicationuser interface 108. Similarly, upon receiving a request to execute thesecond application 86, the application executing component 164 mayinstantiate and begin executing an instance of the second application86, and may deliver to the computer 22 a second application interface110. A third application interface 166 may also be received from anotherapplication host, and may be presented to the user 20 alongside theapplication user interfaces of the first application 80 and the secondapplication 86 (e.g., within a web page embedding all three applicationuser interfaces.) Moreover, the application interfaces are associatedwith the distinct subdomains allocated by the application registeringcomponent 162; e.g., the first application user interface 108 isassociated with the “app1.host1.com” distinct subdomain, while thesecond application interface 110 is associated with the “app2.host1.com”distinct subdomain.

Thereafter, the computer 22 may issue various requests to the respectiveapplications 16 of respective application hosts 12 to perform certainoperations; e.g., the user 20 may, through the first application userinterface 108, request the first application 80 executing on theapplication host 12 to perform an operation, such as accessing a userresource stored on the application host 12. Accordingly, the computer 22may generate and send to respective application hosts 12 variousrequests to be handled by the applications 16 executing thereupon. Dueto the allocation of distinct subdomains by the application registeringcomponent 162, such requests may be handled in an expedient manner thatpromotes two-way isolation of the applications 16. For example, a firstrequest 168 may be generated by the first application user interface 108to be executed by the first application executable 154. Because thefirst request 168 is generated by the first application user interface108, it is associated with the same subdomain as associated with thefirst application user interface 108, i.e., the “app1.host1.com”subdomain. The computer 22 thereby implements a cross-domain restrictionpolicy check of the first request 168, and because the first request 168is directed to an application 80 associated with the same distinctsubdomain, the computer 22 permits the first request 168 to issue. Thefirst request 168 is thereby delivered over the network 24, whereby theaddressing of the first request 168 is translated by a domain nameservice (DNS). Due to the mapping of the distinct subdomain by theapplication registering component 162, the first request 168 isdelivered to the same IP address as the application host 12, i.e.,207.46.30.34, and is accordingly routed to the first application host12. Upon receiving the first request 168, the application host 12 maydetermine that the first request 168 was addressed to the“app1.host1.com” subdomain, and may deliver it to the first application80 for execution. The first request 168 is therefore permitted by thecross-domain restriction policy of the computer 22. Moreover, this firstrequest 168 may be efficiently routed to the application host 12 in theabsence of a specific DNS entry corresponding to the distinct subdomainof the first application 80.

FIG. 5 also presents some contrasting processing of other requests thatillustrate the isolation advantages of the exemplary system 14. As afirst example, the first application user interface 108 may attempt toissue a second request 170 that is actually directed to the secondapplication 86. However, the second request 170 is addressed to thedistinct subdomain of the second application 86 at “app2.host1.com”,which does not match the “app1.host1.com” distinct subdomain associatedwith the first application user interface 108. Therefore, the computer22 prohibits the issuing of the second request 170 as a violation of thecross-domain restriction policy, thereby preventing the firstapplication user interface 108 to violate the isolation of the secondapplication 86. As a second example, the second application interface110 may issue a third request 172 addressed to the second application86, which passes the cross-domain restriction policy of the computer 22and is delivered to the second application 86 over the network 24.Again, the domain name service server 176 may efficiently route thethird request 172 to the application host 12, even in the absence of aspecific DNS entry for the “app2.host1.com” distinct subdomain. As athird example, the third application interface 166 may issue a fourthrequest 174 to the third application executing on a differentapplication host 12 (e.g., hosted at “app3.host2.com”). While thisfourth request 174 may satisfy the cross-domain restriction policy ofthe computer 22, the fourth request 174 may be correctly routed by thenetwork 24 away from the application host 12, thereby preventing anytampering with the first application 80 or the second application 86 bythe third application interface 166. As a fourth example, theapplication interfaces executing on the computer 22 are prevented frominterfering with each other; e.g., an application interface embedded ina web page may access neither the HTML elements of the other applicationinterfaces nor locally stored user resources (such as browser cookies),which are associated with different subdomains. These examplesillustrate some advantages of the exemplary system 152, including theaccessibility of the collective resources of an application 16, thetwo-way isolation of an application 16 from other applications 16 acrossthis model, and the efficiency of handling the routing of such requests(even in view of a large number of distinct subdomains) due to the DNSmapping performed by the application registering component 162.

FIG. 6 illustrates another embodiment 180 of the techniques discussedherein, comprising a computer-readable medium comprisingprocessor-executable instructions configured to implement an exemplarysystem such as described herein (such as the exemplary system 152 ofFIG. 5.) The exemplary computer-readable medium illustrated in FIG. 6comprises a computer-readable medium 182 (e.g., a CD-R, DVD-R, or aplatter of a hard disk drive), on which is encoded computer-readabledata 184. This computer-readable data 184 in turn comprises a set ofcomputer instructions 186 that, when executed by at least one processorof a system, cause the at least one processor to execute an applicationon behalf of a user of a computer (e.g., with reference to FIG. 5, bycausing an application host 12 to execute the first application 80stored in the application store 14 on behalf of the user 20 of thecomputer 22.) In one such embodiment 180, the computer instructions 186might cause the at least one processor to execute the application bystoring 192 the application in the application store; by allocating 194a distinct subdomain of the system for the application mapped to thenetwork address of the system; and, upon receiving 196 a request toexecute the application on behalf of the user, by executing 198 theapplication on the system and presenting 200 to the user an applicationuser interface of the application served from the distinct subdomain. Inanother such embodiment (not shown), the processor-executableinstructions 186 may be configured to implement a system configured toexecute an application 16 on behalf of a user of a computer connected tothe system over a network, which may include, e.g., an application store14 configured to store the application 16; an application registeringcomponent 162 configured to allocate a distinct subdomain 158 of thesystem for the application 16 that is mapped to the network address ofthe system; and an application executing component 164 that isconfigured to execute the application 16 on the system, and to presentto the user an application user interface of the application 16 servedfrom the distinct subdomain 158. Many such computer-readable media maybe devised by those of ordinary skill in the art that are configured tooperate in accordance with the techniques presented herein.

The techniques discussed herein may be devised with variations in manyaspects, and some variations may present additional advantages and/orreduce disadvantages with respect to other variations of these and othertechniques. Moreover, some variations may be implemented in combination,and some combinations may feature additional advantages and/or reduceddisadvantages through synergistic cooperation. The variations may beincorporated in various embodiments (e.g., the exemplary system 152 ofFIG. 5) to confer individual and/or synergistic advantages upon suchembodiments.

A first aspect that may vary among embodiments of these techniquesrelates to the configuration of the components of an exemplary system(such as the exemplary system 152 of FIG. 5) that implement thetechniques presented herein. As a first example of this first aspect,the application store 14 may be configured in many ways to store theapplication. In a first such embodiment, the application store 14comprises a portion of a filesystem of the application host 12, such asan assembly cache that is configured to store application executables(such as scripts, binaries, and application configuration information)and application resources (such as media objects, documentation, anddata sources consumed by the application.) In a second such embodiment,the application store 14 comprises a portion of volatile or non-volatilesystem memory configured to store applications 16 that are currentlyexecuting on the application host 12, that are available for executionon the application host 12, and/or that have recently been executed onthe application host 12.

As a second example of this first aspect, the application registeringcomponent 162 may be configured in many ways to allocate distinctsubdomains for respective applications 16 that are mapped to the networkaddress of an application server 12. In a first such embodiment, theapplication registering component 162 may fulfill the application ofsubdomains mapped to the application host 12 by communicating with adomain name service (DNS) provided by a domain name service serverdisposed on the network over which requests to access such applications16 might be received. Upon receiving a request to make a new application16 available on the application host 12, the application registeringcomponent 162 may send a request to the DNS server to create an entry inthe DNS routing table that maps the subdomain to the network address ofthe application host 12. Subsequent requests to access the application16 may then be handled by the domain name service server according torouting services. In one particular embodiment, the applicationregistering component 162 might configure the domain name service serverto route all subdomains matching a particular pattern (e.g.,“app*.host.com”) to the application host 12. This technique might beadvantageous by reducing the per-application registration of subdomainsby the application registering component 162 and by reducing thecomplexity of the routing rules of the domain name service server 176,thereby economizing the computing resources thereof. However, thistechnique might disadvantageously permit the routing of invalid requeststo the application host 12, e.g., requests specifying subdomains that donot correspond to available applications 16.

In a second embodiment of this second example, the applicationregistering component 162 may operate according to network addresstranslation (NAT) principles for translating requests received over anetwork accessible to the application host 12. For example, theapplication registering component 162 may maintain an internal list ofdistinct subdomains allocated for applications 16 that are available onthe application host 12. When the application host 12 receives a requestto make a new application 16 available, this application registeringcomponent 162 may allocate to the application 16 a distinctive domainand may create a new entry in the list for the application 16. When theapplication registering component 162 later receives a request over thenetwork referencing a subdomain that might correspond to an application16, the application registering component 162 may attempt to locate thesubdomain within the internal list. If the subdomain is located, theapplication registering component 162 might return a network address(e.g., the IP address) of the application host 12 hosting theapplication 16; but if the subdomain is not located in the internallist, the application registering component 162 might refuse the request(e.g., by returning an HTTP 404 error message.) In this manner, theapplication registering component 162 may satisfy the allocation ofdomains according to network address translation techniques. While thisembodiment may more correctly route requests for particular applications16 and may reject requests for unallocated subdomains, this approachmight impose a greater computational burden on the domain name serviceserver 176, such as by expanding the number of routing rules in therouting table utilized by the domain name service server 176.

As a third example of this first aspect, the application executingcomponent 164 may comprise many components on the application host 12that execute the application 16 on behalf of the user 20 and/or thecomputer 22 of the user 20. In a first such embodiment, the applicationexecuting component 164 may comprise a runtime on the application host12 that is configured to load and execute one or more executables thatspecify the logic of the application. In a second such embodiment, theapplication executing component 164 may comprise a script interpreterthat executes server-side scripts comprising the application 16, e.g., aJavaScript parser or Perl interpreter. In a third such embodiment, theapplication executing component 164 may comprise a virtual machineconfigured to execute the application 16, such as a Java virtual machinewithin which a Java-based application 16 may be executed in a safemanner. Those of ordinary skill in the art may devise manyconfigurations of the components of systems that implement thetechniques discussed herein.

A second aspect that may vary among embodiments of these techniquesrelates to additional security and access techniques that may supplementthe exemplary system 152 of FIG. 5. While the exemplary system 152promotes the isolation of an application 16 from other applications 16,this isolation may be further promoted with additional configuration ofan implementation of these techniques. As a first example, additionalmeasures may be taken to promote the isolation of an application userinterface 34 from tampering by other applications. In one such scenario,an application user interface 34 of an application 16 may be embedded ina web page 54, such as a series of references specified in variouselements of the document object model of the web page 54. Otherapplications embedded in the same web page 54 or executing concurrentlywithin the web browser 50 may attempt to interact with the elements ofthe web page 54 comprising the application user interface 34 of theapplication 16 (e.g., detecting the state of controls, detecting ormodifying the contents of variables, or interfering with the contents orexecution of scripts.) In order to promote the isolation of theapplication 16, the application executing component 164 may beconfigured to present the element of the application user interface 34within an isolation construct that is configured to isolate suchelements from other applications 16. As one such example, the elementsof a web application may be specified within an IFRAME HTML element thatis associated with the distinct subdomain that has been allocated forthe application 16 by the application registering component 162. TheIFRAME HTML element may therefore be treated by the web browser 50rendering the web page 54 in accordance with a cross-domain restrictionpolicy (such as the same origin policy) that limits access to suchelements to the application 16 associated with the distinct subdomain.Other scenarios may feature similar isolation constructs provided inaccordance with other programming languages, platforms, and computingtechnologies (e.g., a protected memory section that is accessible onlyto a particular process, or similar element isolation mechanisms thatmay be available in other application user interface models, such asXAML.)

As a second example of this second aspect, the application registeringcomponent 162 may apply other criteria in the allocation of distinctsubdomains for applications 16. In the exemplary scenario 150 of FIG. 5,it may be appreciated that while the allocation of distinct subdomainson a per-application basis may promote two-way isolation of the firstapplication 80 from the second application 86, it might not promote anisolation among instances of a particular application 16. As a firstexample, a user 20 may wish to execute multiple instances of theapplication 16 (either concurrently or consecutively), and it may beadvantageous to isolate a particular instance of the application 16 fromother instances of the same application 16. As a second example, it maybe desirable to implement two-way isolation of a first instance of anapplication 80 executed by a first user from a second instance of theapplication 80 executed on the same computer by a second user. This maybe relevant, e.g., where two users of the same computer systemconcurrently access the application 16, thereby leading to two executingprocesses on the computer 22 that may be able to interact, potentiallycreating a security issue. Accordingly, the application registeringcomponent 162 may be configured to allocate a first distinct subdomainof the application host 12 for a first instance of the application 16,and a second distinct subdomain of the application host 12 for a secondinstance of the application 16. Distinct subdomains may be allocated inmany ways, such as per user of the application (e.g.,user1.app1.host1.com), per computer on which the application userinterface is presented (e.g., computer1.app1.host1.com), and/or perinstance of the application executed by any user (e.g.,instance1.app1.host1.com). Moreover, the application executing component164 may be configured to associate the first instance of the application16 with the first distinct subdomain, and to associate the secondinstance of the application 16 with the second distinct subdomain, etc.This variation may promote the two-way isolation of various instances ofthe application 16.

As a third example of this second aspect, an application executingcomponent 164 may be configured to, upon receiving a request to executean application 16, perform some authentication before executing theapplication 16. In one such variation, the application host 12 mayendeavor to authenticate the identity of the user 20 on whose behalf theapplication 16 is executed, such as according to at least one userauthentication credential received from the user 20 (e.g., a username,password, shared secret, cryptographic authentication, biometricmeasurement, etc.) In one such set of embodiments, the computer 22 ofthe user 20 may be configured to store an authentication token that hasbeen issued by an authenticating service upon authenticating theidentity of the user 20. In one such embodiment, the application host 12might fulfill this role by soliciting user authentication credentialsfrom the user 20, e.g., by presenting to the user 20 a user logininterface configured to receive from the user 20 at least one user logincredential (such as a username and password.) Upon verifying the userauthentication credentials, the application host 12 might generate atleast one user authentication credential and send it to the computer 22,such as an authentication token issued by the application host 12 toverify the identity of the user 20. This authentication token might thenbe provided by the computer 22 with each request submitted to theapplication host 12, such as executing the application 16. Theapplication host 12 may then verify the user authentication token beforeexecuting the application 16. In a second variation, the applicationhost 12 may endeavor to authenticate the application 16 according to atleast one application authentication credential received from theapplication 16. As a first example, the application host 12 may be ableto access a binary hashcode provided by the application developer thatverifies the identity of the application 16 and confirms that itscontents have not been modified. As a second example, the applicationhost 12 may authenticate an application user interface 34 executing onthe computer 22 before fulfilling requests received therefrom, e.g.,according to a shared-secret system or challenge/response asymmetric keysystem, whereby only the application user interface 34 having access tothe shared secret or private key may be able to provide a correctresponse that authenticates the application 16. Those of ordinary skillin the art may devise many techniques for promoting the authenticationof the user 20, computer 22, application 16, etc., and the addition ofother isolation and security features, while implementing the techniquesdiscussed herein.

A third aspect that may vary among embodiments of these techniquesrelates to the interaction of the application 16 with a computingenvironment of the user 20. While some primitive applications 16 (suchas some web applications 46) may execute in complete isolation of thecomputing environment of the user 20, other applications 16 maydesirably interact with some aspects of the computing environment. As afirst example, a user 20 may wish to author a document with an officeproductivity application, and may wish to save the document in the localfilesystem of the computer for access by other applications;accordingly, the application 16 may be permitted to access the localfilesystem to store the data object. As a second example, an application16 may interact with various components of the computer, such as devices(e.g., a media application accessing a portable media device), hardwarecomponents (e.g., a high-quality graphics application accessing adisplay adapter), software APIs (e.g., an enterprise applicationinteracting with distributed resources), locally represented useraccounts, application and operating system configuration information,etc.

Moreover, the nature of the computing environment may differsignificantly among embodiments of these techniques. As one suchexample, the computing environment may exist only on the computer, whichmay also operate as the computing environment host. Alternatively, thecomputing environment may be distributed across several computers anddevices in an uncoordinated or peer-to-peer manner; e.g., theapplication may execute within a virtual environment on a firstcomputer, but may access a portion of the computing environment storedon another computer. As another alternative, the computing environmentmay represent a deployable computing environment that is deployed to aset of computers and devices and centrally managed by a computingenvironment host. In order to reduce the complex variety anddecentralization of the data objects comprising a contemporary computingenvironment, a deployable representation of the computing environmentmay be devised, where the data objects comprising the computingenvironment are organized in a data object hierarchy, which may behosted by a computing environment host. If the data objects arerepresented in a uniform manner and managed in a consistent way by adata object system, a set of services may be devised to apply to alldata objects of the computing environment. The data object hierarchy maybe delivered to various devices to represent the same computingenvironment (including the same user profiles, applications, data files,etc.), and each device may render the computing environment in aconsistent manner but customized based on the capabilities of the device(e.g., a hard keyboard interface for receiving data entry from akeyboard device attached to a workstation, and a touchscreen softwarekeyboard interface for receiving data entry from a cellphone device.) Itmay also be advantageous to configure at least one server to manage oneor more data objects within the representation, and to accept operationssets (e.g., sets of Create, Read, Update, and Delete operations) to beapplied to such data objects. A user of the deployable computingenvironment may therefore interact with the deployable computingenvironment in a platform- and device-independent manner.

FIG. 7 illustrates one such scenario 210, wherein the computingenvironment may be hosted by a computing environment host 212, which maystore and manage a deployable computing environment 214. The computingenvironment host 212 may also render the deployable computingenvironment 214 in different ways on behalf of various devices, such asa cellphone device 216, a personal notebook computer 220, and a publicworkstation 224, and also on behalf of different types of users havingdifferent access privileges. The rendering of the computing environmenttherefore reflects a consistent computing environment across all devicesthat expose the same applications, user profiles, shell configuration,user data objects, etc. Thus, a user may access a full-featured version222 of the computing environment through a high-performance notebookcomputer, a stripped-down version 218 of the computing environment on alow-power cellphone device 216, and a browser-compatible andprivacy-oriented version 88 of the computing environment through a webbrowser 226 of a public workstation 224. To the extent that thecapabilities of each such device support the rendering of the computingenvironment, a consistent user interface and data set may be presenteddue to the rendering of the deployable computing environment 214adjusted to the capabilities of each device. Updates to the computingenvironment may be propagated back to the computing environment host212, and may be automatically synchronized with other devices.

The various devices illustrated in FIG. 7 may also cooperate by sharinglocally stored data with other devices, and by controlling or beingcontrolled by other devices. Hence, the computing environment maytherefore be devised and presented as a cloud computing architecture,comprising a device-independent representation (a “cloud”) expressed asa consistent rendering across all devices (“clients”) that form a meshof cooperating application user interfaces (with device-specificproperties) to the same computing environment. Specifically with respectto the applications of the computing environment, the deployablecomputing environment 214 may include a representation of theapplication set, the application resources, and the data objects createdthereby. Moreover, the computing environment host 212 may apply servicesto the various objects comprising the deployable computing environment214, and the common format in which the data objects are stored in thedeployable computing environment 214 may facilitate consistentavailability and application of the services regardless of the nature ofthe data objects applied thereto. However, those of ordinary skill inthe art may devise many types of computing environments and computingenvironment hosts that may be incorporated in the techniques discussedherein.

Where these techniques are utilized in regard to applications 16 thatmay access a computing environment (whether or not administered by acomputing environment host 212), additional advantages may be achievedby configuring the techniques in view of such accesses. As a firstexample, the exemplary system 152 may be configured to permit users 20to specify the permissions of an application 16 to interact with thecomputing environment, and to enforce such permissions by verifying thepermission credentials of an application 16 before fulfilling any accessrequest. In one such embodiment, the application 16 may comprise atleast one operation applicable to the computing environment of the user20 according to at least one permission (e.g., a permission authorizedby the user 20 for the application 16 to access one or more data object,such as read-only access to a particular file in the filesystem orread/write access to a particular set of data objects or to a particularlocation.) The computer 22 of the user 20 may be configured to storepermission tokens that respectively represent a permission to apply theoperation(s) of the application 16 to the computing environment of theuser 20, and the application executing component 164 may be configuredto validate the permission token before applying the operation to thecomputing environment of the user 20. For example, a user 20 may possessa private key in an asymmetric key pair system. Upon authorizing anapplication 16 to perform a particular type of operation accessing thecomputing environment, the computer 22 of the user 20 may generate andstore a permission token indicating the authorization of thispermission, and may cryptographically sign this permission token withthe private key of the user 20. Later, when the application executingcomponent 164 receives a request from the application 16 to apply theoperation to the computing environment, the application executingcomponent 164 may receive the permission token from the application 16(e.g., from the computer 22 hosting the application user interface 34 ofthe application 16), and may validate the permission token beforeapplying the operation to the computing environment of the user 20. Inone such embodiment, the permission token may comprise a permissioncookie, which may be stored in a browser cache 60 of a web browser 50that may be delivered to the application host 12 along with any requestissued by the user 20 to the application 16 through the application userinterface 34. Additionally, the application host 12 may be involved inthe permission token model, e.g., by receiving from the user anauthorization of the permission to apply the operation of theapplication 16 to the computing environment, and in response generatingthe permission token indicating such permissions and sending suchpermission tokens to the computer 20.

As a second example of this third aspect, the application host 12 maypermit the user 20 to create a computing environment by selectingapplications 16 to be installed, and may install the applications 16within the computing environment for presentation within an aggregatedapplication user interface, such as a desktop that includes separateapplication user interfaces for separate applications 16 that mayexecute concurrently on the application host 12. In this set ofexamples, the exemplary system 152 may include an application installingcomponent, which may be configured to, upon receiving a request from theuser 20 to install an application 16, install the application 16 withinthe computing environment of the user 20. Alternatively or additionally,the exemplary system 14 may include an application cataloging component,which may be configured to present to the user 20 at least oneapplication 16 stored in the application store 14 and installable withinthe computing environment of the user 20 (e.g., a set of applications 16that the application host 12 permits the user to select for installationand execution within the user's computing environment.) Alternatively oradditionally, the exemplary system 152 may include an applicationreceiving component, which may be configured to, upon receiving anapplication 16 from an application developer, store the application 16in the application store 14, and to invoke the application registeringcomponent 162 to allocate the distinct subdomain of the application host12 for the application 16. Moreover, upon receiving this application,the application receiving component 162 might also issue to theapplication 16 at least one application authentication credential, whichmight be provided by the application 16 (e.g., the application userinterface 34 executing on the computer 22) in order to authenticate theapplication 16. Alternatively or additionally, the application host 12might be configured to promote the authorization of the application 16to access the computing environment. For example, if an applicationinvolves at least one operation applicable to the computing environmentof the user 20 that may be performed only with the permission of theuser 20, the application host 12 might identify such permissions uponinstalling the application 16, and may query the user 20 to authorizesuch permissions. In one such embodiment, the application installingcomponent might be configured, while installing the application 16, topresent to the user 20 at least one permission request query requestingan authorization of the permission of the application 16, and uponreceiving the authorization from the user, to store the authorization(e.g., as a permission token stored in a browser cache of a web browseron the computer 22.) Those of ordinary skill in the art may devise manyways of configuring the application host 12 to interact with thecomputing environment of a user on behalf of applications 16 accordingto the techniques discussed herein.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

As used in this application, the terms “component,” “module,” “system”,“interface”, and the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware, software, or software in execution. For example, a componentmay be, but is not limited to being, a process running on a processor, aprocessor, an object, an executable, a thread of execution, a program,and/or a computer. By way of illustration, both an application runningon a controller and the controller can be a component. One or morecomponents may reside within a process and/or thread of execution and acomponent may be localized on one computer and/or distributed betweentwo or more computers.

Furthermore, the claimed subject matter may be implemented as a method,apparatus, or article of manufacture using standard programming and/orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer program accessible from anycomputer-readable device, carrier, or media. Of course, those skilled inthe art will recognize many modifications may be made to thisconfiguration without departing from the scope or spirit of the claimedsubject matter.

FIG. 8 and the following discussion provide a brief, general descriptionof a suitable computing environment to implement embodiments of one ormore of the provisions set forth herein. The operating environment ofFIG. 8 is only one example of a suitable operating environment and isnot intended to suggest any limitation as to the scope of use orfunctionality of the operating environment. Example computing devicesinclude, but are not limited to, personal computers, server computers,hand-held or laptop devices, mobile devices (such as mobile phones,Personal Digital Assistants (PDAs), media players, and the like),multiprocessor systems, consumer electronics, mini computers, mainframecomputers, distributed computing environments that include any of theabove systems or devices, and the like.

Although not required, embodiments are described in the general contextof “computer readable instructions” being executed by one or morecomputing devices. Computer readable instructions may be distributed viacomputer readable media (discussed below). Computer readableinstructions may be implemented as program modules, such as functions,objects, Application Programming Interfaces (APIs), data structures, andthe like, that perform particular tasks or implement particular abstractdata types. Typically, the functionality of the computer readableinstructions may be combined or distributed as desired in variousenvironments.

FIG. 8 illustrates an example of a system 230 comprising a computingdevice 232 configured to implement one or more embodiments providedherein. In one configuration, computing device 232 includes at least oneprocessing unit 236 and memory 238, which may be configured, e.g., tostore instructions implementing the exemplary system 152 of FIG. 5.Depending on the exact configuration and type of computing device,memory 238 may be volatile (such as RAM, for example), non-volatile(such as ROM, flash memory, etc., for example) or some combination ofthe two. Such memory 238 might include, e.g., the application store 14of an exemplary system 152 implementing these techniques 234.

In other embodiments, device 232 may include additional features and/orfunctionality. For example, device 232 may also include additionalstorage (e.g., removable and/or non-removable) including, but notlimited to, magnetic storage, optical storage, and the like. Suchadditional storage is illustrated in FIG. 8 by storage 22240. In oneembodiment, computer readable instructions to implement one or moreembodiments provided herein may be in storage 22240. Storage 22240 mayalso store other computer readable instructions to implement anoperating system, an application program, and the like. Computerreadable instructions may be loaded in memory 238 for execution byprocessing unit 236, for example.

The term “computer readable media” as used herein includes computerstorage media. Computer storage media includes volatile and nonvolatile,removable and non-removable media implemented in any method ortechnology for storage of information such as computer readableinstructions or other data. Memory 238 and storage 22240 are examples ofcomputer storage media. Computer storage media includes, but is notlimited to, RAM, ROM, EEPROM, flash memory or other memory technology,CD-ROM, Digital Versatile Disks (DVDs) or other optical storage,magnetic cassettes, magnetic tape, magnetic disk storage or othermagnetic storage devices, or any other medium which can be used to storethe desired information and which can be accessed by device 232. Anysuch computer storage media may be part of device 232.

Device 232 may also include communication connection(s) 246 that allowsdevice 232 to communicate with other devices. Communicationconnection(s) 246 may include, but is not limited to, a modem, a NetworkInterface Card (NIC), an integrated network interface, a radio frequencytransmitter/receiver, an infrared port, a USB connection, or otherinterfaces for connecting computing device 232 to other computingdevices.

Communication connection(s) 246 may include a wired connection or awireless connection. Communication connection(s) 246 may transmit and/orreceive communication media. The communication connection(s) 246 may beinvolved, e.g., in the network communication of the application host 12with users 20 and computers 22 operated thereby; in the receipt ofapplications 16 to be made available on the application host 12; and/orin the allocation of subdomains mapped to the network address of theapplication host 12.

The term “computer readable media” may include communication media.Communication media typically embodies computer readable instructions orother data in a “modulated data signal” such as a carrier wave or othertransport mechanism and includes any information delivery media. Theterm “modulated data signal” may include a signal that has one or moreof its characteristics set or changed in such a manner as to encodeinformation in the signal.

Device 232 may include input device(s) 244 such as keyboard, mouse, pen,voice input device, touch input device, infrared cameras, video inputdevices, and/or any other input device. Output device(s) 242 such as oneor more displays, speakers, printers, and/or any other output device mayalso be included in device 232. Input device(s) 244 and output device(s)242 may be connected to device 232 via a wired connection, wirelessconnection, or any combination thereof. In one embodiment, an inputdevice or an output device from another computing device may be used asinput device(s) 244 or output device(s) 242 for computing device 232.

Components of computing device 232 may be connected by variousinterconnects, such as a bus. Such interconnects may include aPeripheral Component Interconnect (PCI), such as PCI Express, aUniversal Serial Bus (USB), firewire (IEEE 1394), an optical busstructure, and the like. In another embodiment, components of computingdevice 232 may be interconnected by a network. For example, memory 238may be comprised of multiple physical memory units located in differentphysical locations interconnected by a network.

Those skilled in the art will realize that storage devices utilized tostore computer readable instructions may be distributed across anetwork. For example, a computing device 250 accessible via network 248may store computer readable instructions to implement one or moreembodiments provided herein. Computing device 232 may access computingdevice 250 and download a part or all of the computer readableinstructions for execution. Alternatively, computing device 232 maydownload pieces of the computer readable instructions, as needed, orsome instructions may be executed at computing device 232 and some atcomputing device 250.

Various operations of embodiments are provided herein. In oneembodiment, one or more of the operations described may constitutecomputer readable instructions stored on one or more computer readablemedia, which if executed by a computing device, will cause the computingdevice to perform the operations described. The order in which some orall of the operations are described should not be construed as to implythat these operations are necessarily order dependent. Alternativeordering will be appreciated by one skilled in the art having thebenefit of this description. Further, it will be understood that not alloperations are necessarily present in each embodiment provided herein.

Moreover, the word “exemplary” is used herein to mean serving as anexample, instance, or illustration. Any aspect or design describedherein as “exemplary” is not necessarily to be construed as advantageousover other aspects or designs. Rather, use of the word exemplary isintended to present concepts in a concrete fashion. As used in thisapplication, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or”. That is, unless specified otherwise, or clearfrom context, “X employs A or B” is intended to mean any of the naturalinclusive permutations. That is, if X employs A; X employs B; or Xemploys both A and B, then “X employs A or B” is satisfied under any ofthe foregoing instances. In addition, the articles “a” and “an” as usedin this application and the appended claims may generally be construedto mean “one or more” unless specified otherwise or clear from contextto be directed to a singular form.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure which performs thefunction in the herein illustrated exemplary implementations of thedisclosure. In addition, while a particular feature of the disclosuremay have been disclosed with respect to only one of severalimplementations, such feature may be combined with one or more otherfeatures of the other implementations as may be desired and advantageousfor any given or particular application. Furthermore, to the extent thatthe terms “includes”, “having”, “has”, “with”, or variants thereof areused in either the detailed description or the claims, such terms areintended to be inclusive in a manner similar to the term “comprising.”

What is claimed is:
 1. A system configured to execute an application onbehalf of a user of a computer connected to the system over a network,the system having a network address and comprising: an application storeconfigured to store the application; an application registeringcomponent configured to allocate a distinct subdomain of the system forthe application mapped to the network address of the system; and anapplication executing component configured to, upon receiving a requestto execute the application on behalf of the user: execute theapplication on the system, and present to the user an application userinterface of the application served from the distinct subdomain.
 2. Thesystem of claim 1: the system comprising a web application server; theapplication comprising a web application; the computer of the userhaving a web browser; and the application user interface comprising aweb page embedding the application sent to the computer, the web page tobe rendered in the web browser.
 3. The system of claim 2, theapplication executing component configured to present to the user theapplication user interface within the web browser within an isolationconstruct configured to isolate the application user interface fromother applications executing on the computer.
 4. The system of claim 3,the isolation construct comprising a hypertext markup language IFRAMEelement associated with the distinct subdomain allocated for theapplication.
 5. The system of claim 1: the system configured to executea first instance of the application and a second instance of theapplication; the application registering component configured to:allocate a first distinct subdomain of the system for the first instanceof the application mapped to the network address of the system, andallocate a second distinct subdomain of the system for the secondinstance of the application mapped to the network address of the system;and the application executing component configured to: associate thefirst instance of the application with the first distinct subdomain, andassociate the second instance of the application with the seconddistinct subdomain.
 6. The system of claim 5: the first instance of theapplication executed on behalf of a first user, and the second instanceof the application executed on behalf of a second user.
 7. The system ofclaim 1, the application executing component configured, beforeexecuting the application, to authenticate the user according to atleast one user authentication credential received from the user.
 8. Thesystem of claim 7, comprising: a user login interface configured to:present to the user a user login interface configured to receive fromthe user at least one user login credential, and upon receiving from theuser the at least one user login credential: verify the at least oneuser login credential, and upon verifying the at least one user logincredential: generate the at least one user authentication credential,and send to the computer the at least one user authenticationcredential.
 9. The system of claim 1, the application executingcomponent configured to, before executing the application, authenticatethe application according to at least one application authenticationcredential received from the application.
 10. The system of claim 1, thesystem having access to a computing environment store configured tostore at least one data object comprising a computing environment of theuser.
 11. The system of claim 10: the application comprisinginstructions configured to perform at least one operation applicable tothe computing environment of the user according to at least onepermission; the computer of the user configured to store at least onepermission token representing a permission to apply the at least oneoperation of the application to the computing environment of the user;and the application executing component configured to execute theapplication by: receiving the at least one permission token with therequest to execute the application on behalf of the user; validating theat least one permission token; and upon validating the at least onepermission token, applying the operation of the application to thecomputing environment of the user.
 12. The system of claim 11: thesystem comprising a web application server; the application comprising aweb application; the at least one permission token comprising apermission cookie; and the computer of the user having a web browserconfigured to: store the permission cookie, and send the permissioncookie to the web application server with the request to execute theapplication.
 13. The system of claim 11, the system comprising: apermission token generating component configured to, upon receiving fromthe user an authorization of the permission to apply the at least oneoperation of the application to the computing environment: generate thepermission token indicating the permission to apply the at least oneoperation of the application to the computing environment, and send thepermission token to the computer.
 14. The system of claim 10,comprising: an application installing component configured to, uponreceiving a request from the user to install the application, installthe application within the computing environment of the user.
 15. Thesystem of claim 14, comprising: an application cataloging componentconfigured to present to the user at least one application stored in theapplication store and installable within the computing environment ofthe user.
 16. The system of claim 14, comprising: an applicationreceiving component configured to, upon receiving an application from anapplication developer: store the application in the application store,and invoke the application registering component to allocate thedistinct subdomain of the system for the application.
 17. The system ofclaim 16, the application receiving component configured to, uponreceiving the application from the application developer, issue to theapplication at least one application authentication credential.
 18. Thesystem of claim 14: the application instructions configured to performat least one operation applicable to the computing environment of theuser according to at least one permission, and the applicationinstalling component configured, while installing the application onbehalf of the user, to: present to the user at least one permissionrequest query requesting an authorization of the permission of theapplication, and upon receiving the authorization from the user, storethe authorization.
 19. A computer-readable storage medium, the mediumcomprising instructions that, when executed by at least one processor ofa system connected to a network and having a network address and anapplication store, cause the at least one processor to execute anapplication on behalf of a user of a computer by: storing theapplication in the application store; allocating a distinct subdomain ofthe system for the application mapped to the network address of thesystem; and upon receiving a request to execute the application onbehalf of the user: executing the application on the system, andpresenting to the user an application user interface of the applicationserved from the distinct subdomain.
 20. A system comprising a webapplication server configured to execute an application comprising a webapplication on behalf of a user of a computer connected to the systemover a network, the system having a network address and having access toa computing environment store configured to store at least one dataobject comprising a computing environment of the user, the applicationinstructions that, when executed by at least one processor of thesystem, cause the at least one processor to execute at least oneoperation applicable to the computing environment of the user accordingto at least one permission, and the system comprising: an applicationstore configured to store the application; an application registeringcomponent configured to allocate a distinct subdomain of the system forthe application mapped to the network address of the system; anapplication installing component configured to, upon receiving a requestfrom the user to install the application, install the application withinthe computing environment of the user; an application catalogingcomponent configured to present to the user at least one applicationstored in the application store and installable within the computingenvironment of the user; an application receiving component configuredto, upon receiving an application from an application developer: storethe application in the application store, and invoke the applicationregistering component to allocate the distinct subdomain of the systemfor the application; a user login interface configured to: present tothe user a user login interface configured to receive from the user atleast one user login credential, and upon receiving from the user the atleast one user login credential: verify the at least one user logincredential, and upon verifying the at least one user login credential:generate the at least one user authentication credential, and send tothe computer the at least one user authentication credential; apermission token generating component configured to, upon receiving fromthe user an authorization of the permission to apply the at least oneoperation of the application to the computing environment: generate thepermission token indicating the permission to apply the at least oneoperation of the application to the computing environment, and send thepermission token to the computer; and an application executing componentconfigured to, upon receiving a request to execute the application onbehalf of the user: authenticate the user according to at least one userauthentication credential received from the user; authenticate theapplication according to the at least one application authenticationcredential received from the application; after authenticating the userand after authenticating the application, execute the application on thesystem by: receiving the at least one permission token with the requestto execute the application on behalf of the user validating the at leastone permission token; and upon validating the at least one permissiontoken, applying the operation of the application to the computingenvironment of the user; and present to the user an application userinterface of the application, comprising a web page embedding theapplication rendered in a web browser of the computer, the applicationuser interface served from the distinct subdomain and presented withinan isolation construct configured to isolate the application userinterface from other applications executing on the computer, theisolation construct comprising a hypertext markup language IFRAMEelement associated with the distinct subdomain allocated for theapplication.